intrauterine growth retardation

Intrauterine Growth Retardation 

Definition

Intrauterine growth retardation (IUGR) occurs when the unborn baby is at or below the 10th weight percentile for his or her age (in weeks).

Description

There are standards or averages in weight for unborn babies according their age in weeks. When the baby's weight is at or below the 10th percentile for his or her age, it is called intrauterine growth retardation or fetal growth restriction. These babies are smaller than they should be for their age. How much a baby weighs at birth depends not only on how many weeks old it is, but the rate at which it has grown. This growth process is complex and delicate. There are three phases associated with the development of the baby. During the first phase, cells multiply in the baby's organs. This occurs from the beginning of development through the early part of the fourth month. During the second phase, cells continue to multiply and the organs grow. In the third phase (after 32 weeks of development), growth occurs quickly and the baby may gain as much as 7 ounces per week. If the delicate process of development and weight gain is disturbed or interrupted, the baby can suffer from restricted growth.

IUGR is usually classified as symmetrical or asymmetrical. In symmetrical IUGR, the baby's head and body are proportionately small. In asymmetrical IUGR, the baby's brain is abnormally large when compared to the liver. In a normal infant, the brain weighs about three times more than the liver. In asymmetrical IUGR, the brain can weigh five or six times more than the liver.

Causes and symptoms

Doctors think that the two types of IUGR may be linked to the time during development that the problem occurs. Symmetrical IUGR may occur when the unborn baby experiences a problem during early development. Asymmetrical IUGR may occur when the unborn baby experiences a problem during later development. While not true for all asymmetrical cases, doctors think that sometimes the placenta may allow the brain to get more oxygen and nutrition while the liver gets less.

There are many IUGR risk factors involving the mother and the baby. A mother is at risk for having a growth restricted infant if she:

• Has had a previous baby who suffered from IUGR
• Is small in size
• Has poor weight gain and nutrition during pregnancy
• Is socially deprived
• Uses substances (like tobacco, narcotics, alcohol) that can cause abnormal development or birth defects
• Has a vascular disease (like preeclampsia)
• Has chronic kidney disease
• Has a low total blood volume during early pregnancy
• Is pregnant with more than one baby
• Has an antibody problem that can make successful pregnancy difficult (antiphospholipid antibody syndrome).

Additionally, an unborn baby may suffer from IUGR if it has:

• Exposure to an infection, including German measles (rubella), cytomegalovirus, tuberculosis, syphilis, or toxoplasmosis
• A birth defect (like a severe cardiovascular defect)
• A chromosome defect, especially trisomy 18 (Edwards' syndrome)
• A primary disorder of bone or cartilage
• A chronic lack of oxygen during development (hypoxia)
• Placenta or umbilical cord defects
• Developed outside of the uterus.

Key terms

Preeclampsia — Hypertension (high blood pressure) during pregnancy.

Diagnosis

IUGR can be difficult to diagnose and in many cases doctors are not able to make an exact diagnosis until the baby is born. A mother who has had a growth restricted baby is at risk of having another during a later pregnancy. Such mothers are closely monitored during pregnancy. The length in weeks of the pregnancy must be carefully determined so that the doctor will know if development and weight gain are appropriate. Checking the mother's weight and abdomen measurements can help diagnose cases when there are no other risk factors present. Measuring the girth of the abdomen is often used as a tool for diagnosing IUGR. During pregnancy, the healthcare provider will use a tape measure to record the height of the upper portion of the uterus (the uterine fundal height). As the pregnancy continues and the baby grows, the uterus stretches upward in the direction of the mother's head. Between 18 and 30 weeks of gestation, the uterine fundal height (in cm.) equals the weeks of gestation. If the uterine fundal height is more than 2-3 cm below normal, then IUGR is suspected. Ultrasound is used to evaluate the growth of the baby. Usually, IUGR is diagnosed after week 32 of pregnancy. This is during the phase of rapid growth when the baby should be gaining more weight. IUGR caused by genetic factors or infection may sometimes be detected earlier.

Treatment

There is no treatment that improves fetal growth, but IUGR babies who are at or near term have the best outcome if delivered promptly. If IUGR is caused by a problem with the placenta and the baby is otherwise healthy, early diagnosis and treatment of the problem may reduce the chance of a serious outcome.

Prognosis

Babies who suffer from IUGR are at an increased risk for death, low blood sugar (hypoglycemia), low body temperature (hypothermia), and abnormal development of the nervous system. These risks increase with the severity of the growth restriction. The growth that occurs after birth cannot be predicted with certainty based on the size of the baby when it is born. Infants with asymmetrical IUGR are more likely to catch up in growth after birth than are infants who suffer from prolonged symmetrical IUGR. However, as of 1998, doctors cannot reliably predict an infant's future progress. Each case is unique. Some infants who have IUGR will develop normally, while others will have complications of the nervous system or intellectual problems like learning disorders. If IUGR is related to a disease or a genetic defect, the future of the infant is related to the severity and the nature of that disorder.

Resources

Books

Cunningham, F. Gary, et al. Williams Obstetrics. 20th ed. Stamford: Appleton & Lange, 1997.

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intrauterine growth retardation

n. Abbr. IUGR

Birth weight that is below the tenth percentile for gestational age. Also called intrauterine growth restriction.

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intrauterine growth retardation,

an abnormal process in which the development and maturation of the fetus are impeded or delayed more than two deviations below the mean for gestational age, sex, and ethnicity. It may be caused by genetic factors, maternal disease, or fetal malnutrition that results from placental insufficiency. See also growth retardation, small for gestational age infant.

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intrauterine

within the uterus.

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intrauterine contraceptive device

a mechanical device inserted into the uterine cavity for the purpose of contraception. These devices, used in human gynecology, have been used in draft cattle in Asia for many years. Used occasionally also in dogs. Called also IUD.

intrauterine growth retardation

failure to grow properly in utero in stature, as measured by crown to rump measurement. Pituitary dwarfism in cattle and runting in piglets and puppies are typical examples.

intrauterine medication

medication applied to the uterus via a cervical catheter, or manually in the recently birthed mare, sow or cow.

intrauterine therapy

is a common practice in food animals. Infusion of fluid material or manual placement of solid materials are the usual methods employed. The method has the advantage of achieving maximum concentration of the medicament at the endometrium but only low concentrations are achieved in the deeper layers. See also infusion.

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intrauterine growth retardation

Fetal growth restriction Neonatology A generic term for any delay in achieving intrauterine developmental milestones, most commonly related to maternal drug, tobacco and alcohol abuse; IUGR affects high-risk infants with perinatal asphyxia, hypoglycemia, hypothermia, pulmonary hemorrhage, meconium aspiration, necrotizing enterocolitis, polycythemia and complications of infections, malformations and syndromes; IUGR fetuses have weight < 10^th percentile for gestational age, abdominal circumference < 2.5^th percentile Types Symmetric–body is proportionately small; asymmetric–head is disproportionately bigger than body, which implies undernourishment–growth of vital organs–heart, brain is at expense of liver, muscle and fat, often due to placental insufficiency; IUGR is the 2^nd most common–after prematurity–cause of perinatal M&M; it affects ±5% of the general obstetric population. See Low birthweight, Small for gestational age.

Intrauterine growth restriction  

Placental insufficiency  

• Unexplained elevated maternal alpha- fetoprotein level

• Idiopathic

• Preeclampsia

• Chronic maternal disease

• Cardiovascular disease

• Diabetes

• Hypertension

Abnormal placentation

• Abruptio placentae

• Placenta previa

• Infarction

• Circumvallate placenta

• Placenta accretia

• Hemangioma

Genetic disorders

• Family history

• Trisomy 13, 18 and 21

• Triploidy

• Turner's syndrome (some cases)

• Malformations

Immunologic

• Antiphospholipid syndrome

Infections

• Cytomegalovirus

• Rubella

• Herpes

• Toxoplasmosis

Metabolic

• Phenylketonuria

Other

• Poor maternal nutrition

• Substance abuse (smoking, alcohol, drugs)

• Multiple gestation

• Low socioeconomic status